JP2010020085A - Optical waveguide structure and method of manufacturing the same, and optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce coupling loss between each optical waveguide of an optical waveguide structure, which is used for connecting a light emitting device and light receiving device to one optical fiber array, and each optical fiber of the optical fiber array or between each optical waveguide and a light emitting device or a light receiving device. <P>SOLUTION: An optical waveguide structure is designed to have a receiving end optical waveguide 7B which connects an optical fiber 33A included in an optical fiber array to a light receiving device and a transmitting end optical waveguide 7A which connects the optical fiber 33A included in the optical fiber array to a light emitting device, wherein the cross section of the core 4B of the receiving end optical waveguide 7B is made larger than the cross section of the core 4A of the transmitting end optical waveguide 7A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical waveguide structure used for, for example, optical communication, and more particularly to an optical waveguide structure suitable for connecting a light emitting device and a light receiving device to the same optical fiber array, a manufacturing method thereof, and an optical module.

In recent years, development of multi-channel optical transceivers (for example, wavelength-division multi-channel optical transceivers) including surface-type optical devices such as surface-emitting lasers (light-emitting devices) and photodiodes (photo-detectors; light-receiving devices) has been promoted.
For example, when using a surface optical device such as a surface emitting laser or a photodiode in an optical module such as a multi-channel optical transceiver, the light incident surface (light receiving surface) or light emitting surface (light emitting surface) of the surface optical device is mounted. Since it is parallel to the substrate, light is incident or emitted perpendicular to the mounting substrate.

On the other hand, it is necessary to reduce the size and thickness of such an optical module.
In order to reduce the size and thickness, it is desirable to arrange the optical fiber (optical fiber array) in parallel with the mounting substrate. In this case, the end face of the optical fiber and the light incident surface or light emitting surface of the surface optical device have a substantially right-angle positional relationship.
For this reason, the optical fiber array and the surface light are bent by approximately 90 degrees in the light path (light path) incident or emitted perpendicular to the light incident surface or light exit surface of the surface optical device mounted on the substrate. It is necessary to optically connect the device.

Therefore, for example, an optical waveguide structure having an optical waveguide (curved waveguide) on a substantially perpendicular curved surface is used for a planar optical device in order to sharply bend the light path in a narrow space in an apparatus such as an optical transceiver. On the other hand, there is a technique in which incident or outgoing light is guided along a curved surface and coupled to an optical fiber array.
In such an optical waveguide structure, a liquid core material is dropped on a curved surface, a film is pasted thereon, and the liquid core material is thinned by pressing with a constant pressure using a soft material such as silicon rubber. Produced by stretching and curing by UV irradiation.
JP 2005-115346 A

By the way, in the optical waveguide structure as described above, the cross-sectional shape of the core (waveguide core) of each optical waveguide is generally rectangular, and the size is the same regardless of the reception side or the transmission side. is there.
The optical waveguide structure as described above is used to connect the light emitting device and the light receiving device to the same optical fiber array. In general, each optical fiber constituting the optical fiber array has the same diameter (fiber diameter; core diameter).

  For example, if the length of one side of the square waveguide core is the same as the diameter of the circular optical fiber, the light of the optical waveguide structure is transmitted in the transmission channel (transmission ch) as shown in FIG. When light emitted from the waveguide (transmission side) enters the optical fiber (transmission side) of the optical fiber array, light from the four corners of the optical waveguide leaks, and light emitted from the optical waveguide of the optical waveguide structure Cannot be coupled to the optical fibers of the optical fiber array without loss.

  Conversely, if the length of the diagonal line of the square waveguide core and the diameter of the circular optical fiber are the same, the light of the optical fiber array is received in the reception channel (reception channel) as shown in FIG. When light emitted from the fiber (receiving side) is incident on the optical waveguide (receiving side) of the optical waveguide structure, light from the periphery of the optical fiber leaks, and light emitted from the optical fiber of the optical fiber array Cannot be coupled to the optical waveguide of the optical waveguide structure without loss.

As described above, on at least one of the transmission side and the reception side, light leaks at the connection portion between the optical waveguide and the optical fiber due to the geometric shape of the optical waveguide and the optical fiber, resulting in coupling loss. I can't avoid it.
Therefore, the coupling loss between each optical waveguide of the optical waveguide structure used to connect the light emitting device and the light receiving device to the same optical fiber array and each optical fiber of the optical fiber array, or each optical waveguide and light emission I want to be able to reduce the coupling loss between devices and light receiving devices.

Therefore, the optical waveguide structure is connected to the receiving side optical waveguide that connects the receiving optical fiber and the light receiving device included in the optical fiber array, and to the transmitting optical fiber that connects the transmitting optical fiber and the light emitting device included in the optical fiber array. It is a requirement that the cross-sectional area of the core of the receiving-side optical waveguide is larger than the cross-sectional area of the core of the transmitting-side optical waveguide.
An optical module is required to include the optical waveguide structure described above.

  An optical waveguide structure manufacturing method includes: a receiving-side optical waveguide connecting a receiving optical fiber included in an optical fiber array and a light receiving device; and a transmitting optical fiber connecting a transmitting optical fiber included in the optical fiber array and a light emitting device. A method of manufacturing an optical waveguide structure including a side optical waveguide, wherein grooves having different sizes on a curved surface are formed so that a cross-sectional area of a core of a receiving-side optical waveguide is larger than a cross-sectional area of a core of a transmitting-side optical waveguide And a step of filling the groove with a liquid core material, covering the groove with a clad film, and curing the liquid core material in a state covered with the clad film. As a requirement.

  Therefore, according to the optical waveguide structure, the manufacturing method thereof, and the optical module, each optical waveguide of the optical waveguide structure and each light of the optical fiber array used to connect the light emitting device and the light receiving device to the same optical fiber array. There is an advantage that the coupling loss between the fibers or the coupling loss between each optical waveguide and the light emitting device or the light receiving device can be reduced.

Hereinafter, an optical waveguide structure according to the present embodiment, a manufacturing method thereof, and an optical module will be described with reference to FIGS.
First, this optical waveguide structure is a curved optical waveguide component (for example, a polymer optical waveguide) formed so that light propagates in a curved waveguide core, and as shown in FIG. A clad structure (lower clad) 1 formed on the curved surface 2 and having a plurality of grooves 3A and 3B (here, a plurality of grooves 3A and 3B of two different sizes) and formed in each of the grooves 3A and 3B Waveguide cores 4A and 4B, and a clad film (upper clad) 5 covering the plurality of waveguide cores 4A and 4B.

  Here, as shown in FIG. 5D, the clad structure 1 has a plurality of grooves (for waveguides) provided in parallel on the curved surface 2 of the surface of the structure, extending from one end of the curved surface 2 to the other end. (Slot; narrow groove) 3A, a curved surface structure having 3B. Here, the cladding structure 1 is a transparent structure formed of a transparent member made of a transparent cladding material, and has a refractive index n1. For example, a molded product (resin molded product) using an olefin polymer (for example, polyolefin).

  As shown in FIG. 5D, the waveguide cores 4A and 4B are formed by embedding the grooves 3A and 3B formed in the curved surface layer portion of the cladding structure 1 with a transparent core material. For this reason, the waveguide cores 4 </ b> A and 4 </ b> B are formed in a curved shape along the curved surface 2 of the clad structure 1 and have a columnar shape. The waveguide cores 4A and 4B have a refractive index n2 larger than the refractive index n1 of the cladding structure 1 (n2> n1).

As will be described later, in this embodiment, the waveguide cores 4A and 4B are formed by applying and curing the liquid core material (liquid adhesive) 4, so that the refractive index after curing is n2. A material (a transparent solid having a refractive index of n2) is used.
The clad film 5 is laminated so as to cover the waveguide cores 4A and 4B formed in the grooves 3A and 3B on the curved surface 2 of the clad structure 1, as shown in FIG. The clad film 5 has a refractive index n3 smaller than the refractive index n2 of the waveguide cores 4A and 4B (n3 <n2).

Such an optical waveguide structure 8 includes, for example, a function (optical transmitter) that converts an input electric signal into an optical signal and transmits the optical signal via an arrayed optical fiber (optical fiber array), and an optical fiber array. Is used for a multi-channel optical transceiver (optical module) having a function (optical receiver) for converting an optical signal input via the optical signal into an electrical signal and receiving the electrical signal.
In this case, as shown in FIG. 4, for example, the multi-channel optical transceiver includes a surface light receiving device array including a printed circuit board (circuit board) 30 and a plurality of surface light receiving devices 31A having an incident surface (light receiving surface) on the surface. 31, a surface light emitting device array 32 including a plurality of surface light emitting devices 32 </ b> A having an emission surface (light emitting surface) on the surface, a driver IC 35, a receiver IC 36, a cladding structure, a waveguide core, and a cladding film. And an optical waveguide structure 8 having a plurality (eight in this case) of curved waveguides 7A and 7B. An optical transceiver with 4 channels on the transmission side and 4 channels on the reception side is taken as an example.

Here, the surface light-receiving device 31A is a photodiode (photo detector; PD; Photo detector), and the surface light-receiving device array 31 is a PD array chip including a plurality (four in this case) of photodiodes.
The surface light emitting device 32A is a surface emitting laser [VCSEL (Vertical-Cavity Surface-Emitting Laser)], and the surface light emitting device array 32 includes a plurality (four in this case) of surface emitting lasers. is there.

  Among the plurality (eight in this case) of curved waveguides provided in the optical waveguide structure 8, some (here, four) curved waveguides 7B are included in the optical fiber array 33 (here The four optical fibers (receiving optical fibers) 33A and the light receiving device 31A are connected to each other and function as a receiving-side optical waveguide (receiving channel), and the remaining (four here) curved waveguides 7A are optical fibers. It functions as a transmission side optical waveguide (transmission channel) that connects the remaining (four in this case) optical fibers (transmission optical fibers) 33A included in the array 33 and the light emitting device 32A. Here, a plurality of reception-side optical waveguides 7B and a plurality of transmission-side optical waveguides 7A are provided in parallel.

  The optical waveguide structure 8 is mounted on the printed circuit board 30 through one end face, and a surface light receiving device array 31 and a surface light emitting device array 32 are provided on the one end face via a lens, for example. An optical fiber array 33 composed of a plurality (here, 12) of optical fibers 33A having the same fiber diameter is optically connected to the other end face orthogonal to the one end face. . Here, the optical fiber array 33 is a ribbon fiber. Here, an optical fiber array 33 with an optical connector 34 is used.

The printed circuit board 30 is electrically connected to an external device via a device-side electrical connector, and an electrical signal is input or output (electrical I / O).
Thus, the present optical waveguide structure 8 connects the surface light emitting device array 32 and the surface light receiving device array 31 to the same optical fiber array 33 in a multi-channel optical transceiver in which the transmission side and the reception side are provided in parallel. Used as a multi-channel optical waveguide adapter.

By the way, in the case of multimode optical transmission, light emitted from the end face of an optical fiber or optical waveguide is at an arbitrary angle within a range defined by a numerical aperture (NA) from an arbitrary point on the surface of the core. It can be expressed as a bundle (light flux) of emitted light rays. It is difficult to focus this light beam on an area narrower than the emitted core surface by using a general lens system.
Therefore, the spot size on the exit surface (core surface) of the optical fiber 33A (or optical waveguides 7A and 7B) is the same as the spot size on the incident surface (core surface) of the optical waveguides 7A and 7B (or optical fiber 33A). In this way, the light is condensed by a lens system [here, a lens denoted by reference numeral 9 in FIG. 2B].

In this embodiment, as shown in FIGS. 1A and 1B, the cross-sectional area of the core (waveguide core; reception core) 4B of the reception side optical waveguide 7B is the core of the transmission side optical waveguide 7A. (Waveguide core; transmission-side core) The cross-sectional area of 4A is made larger.
Specifically, as shown in FIG. 1B, the shortest distance of the cross section of the core 4B of the receiving side optical waveguide 7B (here, since the cross section of the waveguide core 4B is rectangular, the length of its short side) Is equal to or larger than the diameter of the core (circular cross section) of the optical fiber 33A. Further, the longest distance of the cross section of the core 4A of the transmission side optical waveguide 7A (here, the length of the diagonal line of the rectangular cross section) is equal to or smaller than the diameter of the core (circular cross section) of the transmission optical fiber 33A. I have to.

In this way, the optical waveguide structure can be obtained by making the incident-side sectional area larger than the emitting-side sectional area on both the receiving side and the transmitting side (emission-side sectional area <incident-side sectional area). The coupling loss between each optical waveguide 7A, 7B of the body 8 and each optical fiber 33A of the optical fiber array 33 is minimized.
3A, the shortest distance of the cross section of the core 4A of the transmission side optical waveguide 7A (here, since the cross section of the waveguide core 4A is rectangular, the length of the short side) is the light emission. The diameter of the light emitting surface (circular) 32AX of the device 32A is the same as or larger than that. As shown in FIG. 3B, the longest distance of the cross section of the core 4B of the receiving side optical waveguide 7B (here, the length of the diagonal line of the rectangular cross section) is the diameter of the light receiving surface (circular) 31AX of the light receiving device 31A. It is made the same or smaller than that.

In this way, the optical waveguide structure can be obtained by making the incident-side sectional area larger than the emitting-side sectional area on both the receiving side and the transmitting side (emission-side sectional area <incident-side sectional area). The coupling loss between the optical waveguides 7A and 7B of the body 8 and the light emitting device 32A and the light receiving device 31A is minimized.
In the present embodiment, the receiving-side optical waveguide 7B and the transmitting-side optical waveguide 7A both have the same cross-sectional area over the entire length. However, the present invention is not limited to this. It is sufficient that the size of the cross-sectional area satisfying the relationship as described above is sufficient at the connection portion (coupling portion) to the fiber array 33 or the connection portion (coupling portion) to the light emitting device 32A and the light receiving device 31A.

  In the present embodiment, the cross-sectional shape of the cores 4B and 4A of the respective optical waveguides 7A and 7B of the optical waveguide structure 8 is rectangular, but is not limited to this, and may be, for example, elliptical or circular good. In this case, the shortest distance between the cross-sections of the cores 4B and 4A of the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A is the length of the elliptical short axis or the length of the circular diameter. The longest distance of the cross section of the cores 4B, 4A of the transmission side optical waveguide 7A is the length of the major axis of the ellipse or the length of the diameter of the circle.

  Further, as shown in FIGS. 1A and 1B, the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A are provided on the end face on the side to which the optical fiber array 33 is connected, of the optical waveguides 7A and 7B. The central axes X of the cores 4A and 4B are arranged on the same plane, and as shown in FIG. 2B, coincide with the interval between the central axes of the cores of the optical fibers 33A constituting the optical fiber array 33. Is provided.

  Here, in order to form a waveguide array composed of a plurality of optical waveguides 7A and 7B on the surface of the curved surface 2 of the clad structure 1, the central axes of the cores 4A and 4B of these optical waveguides 7A and 7B are the same plane. The depths of the grooves 3A and 3B of the clad structure 1 (the heights of the waveguide cores 4A and 4B) are set so as to line up. In this case, as shown in FIG. 1B, a step 6 is formed on the surface of the clad structure 1 between the reception side optical waveguide 7B and the transmission side optical waveguide 7A.

  Further, the interval (pitch) between the grooves 3A and 3B of the clad structure 1 is set so as to coincide with the interval between the central axes of the cores of the optical fibers 33A of the optical fiber array 33. As a result, the central axes of the cores 4A and 4B of all the optical waveguides 7A and 7B on the reception side and transmission side can be made to coincide with the central axis of the core of each optical fiber 33A of the optical fiber array 33. It is possible to prevent any axial deviation between the optical waveguides 7A and 7B and the optical fiber 33A on either side.

Thereby, connection with the optical fiber array 33 can be performed without loss, and further, a difference in coupling loss between the reception side and the transmission side can be prevented.
In particular, in the present optical waveguide structure 8, since the plurality of waveguide cores 4A and 4B are formed adjacent to each other on the curved surface 2, leakage light from one waveguide core is transferred to another adjacent waveguide core. There is a risk of crosstalk (crosstalk noise). However, by reducing the coupling loss as described above, it is possible to reduce such crosstalk between adjacent channels. As a result, the crosstalk performance can be improved and the reliability can be improved. it can.

Next, a method for manufacturing the optical waveguide structure according to the present embodiment will be described with reference to FIGS.
The optical waveguide structure manufacturing method includes a receiving-side optical waveguide 7B that connects an optical fiber 33A and a light receiving device 31A included in the optical fiber array 33, an optical fiber 33A and a light emitting device 32A that are included in the optical fiber array 33, and the like. 5A is a method for manufacturing an optical waveguide structure 8 including a transmission-side optical waveguide 7A that connects the two, including each step as shown in FIGS.

  First, as shown in FIG. 5A, a curved surface structure having a plurality of grooves (waveguide grooves; narrow grooves) 3A and 3B extending from one end to the other end of the curved surface 2 on the curved surface 2 of the surface of the structure. (Clad structure; transparent structure) 1 is produced by molding using, for example, an olefin-based polymer (polyolefin; a transparent member made of a transparent clad material). That is, the curved surface structure (mold base material: mold optical waveguide) 1 in which the grooves 3A and 3B are previously formed on the curved surface 2 is produced.

Here, two different sizes are provided on the curved surface 2 so that the cross-sectional area of the core 4B of the receiving-side optical waveguide 7B is larger than the cross-sectional area of the core 4A of the transmitting-side optical waveguide 7A [see FIG. The curved surface structure 1 having a plurality of grooves 3A and 3B is prepared.
Next, as shown in FIG. 5B, each groove 3A, 3B on one end side or the other end side of each groove 3A, 3B of the curved surface structure 1 is formed by a dispenser (quantitative dispenser; liquid core material dropping device). A predetermined amount of liquid core material (waveguide core liquid, transparent polymer liquid, transparent liquid, or transparent adhesive) 4 is dropped onto the curved surface 2 that is included.

Next, as shown in FIG. 5C, the clad film (for example, olefin film) 5 is gradually pressed and covered from the side where the liquid core material 4 is dropped toward the opposite side (that is, the clad). While laminating the film 5), the liquid core material 4 is filled in the grooves 3 </ b> A and 3 </ b> B.
Next, as shown in FIG. 5D, the liquid core material is irradiated with, for example, ultraviolet rays while covered with the clad film 5 (that is, with the clad film 5 pressed against the curved surface 2). (For example, UV epoxy resin, ultraviolet curable resin material, or photocurable resin material) 4 is cured (here, semi-cured or temporarily cured).

In this embodiment, since the liquid core material 4 is kept in a semi-cured state at this stage, the liquid core material 4 is completely or substantially completely cured in the subsequent steps. In the present specification, hereinafter, such complete or almost complete curing is referred to as “main curing”.
Here, the liquid core material 4 is cured (semi-cured in this case) by irradiating, for example, ultraviolet rays from the back surface side of the transparent curved structure 1 through the curved structure 1. When a transparent film is used as the clad film 5, the liquid core material 4 may be cured (here, semi-cured) by irradiating, for example, ultraviolet rays through the clad film 5 from the surface side.

Here, the liquid core material 4 is semi-cured at this stage, but the present invention is not limited to this, and it may be fully cured at this stage.
Thereafter, as shown in FIG. 5D, for example, heat is applied to fully cure the liquid core material 4. Thereby, the waveguide cores 4A and 4B are formed.
In this way, the optical waveguide structure 8 including the receiving side optical waveguide 7B and the transmitting side optical waveguide 7A as a plurality of channel-shaped optical waveguides (curved waveguides; optical paths) on the curved surface 2 is manufactured. The optical waveguide structure 8 is a polymer optical waveguide whose main material is a polymer, and is also referred to as an optical waveguide member. The optical waveguide structure 8 optically connects the optical fiber 33A to the light receiving device 31A and the light emitting device 32A, and is also referred to as an optical connecting member.

  Therefore, according to the optical waveguide structure and the manufacturing method thereof according to this embodiment, each optical waveguide 7A of the optical waveguide structure 8 used to connect the light emitting device 32A and the light receiving device 31A to the same optical fiber array 33. , 7B and each optical fiber 33A of the optical fiber array 33, or the coupling loss between each optical waveguide 7A, 7B and the light emitting device 32A or the light receiving device 31A can be reduced. That is, when an optical waveguide structure (optical waveguide adapter) 8 in which the transmission side and the reception side are incorporated in the same component is used, the coupling loss with the standard optical fiber array 33 is minimized on both the transmission side and the reception side. Therefore, a high-performance optical transceiver can be realized. Moreover, the crosstalk performance of such an optical waveguide structure 8 can be improved, and the reliability can be enhanced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
Further, in the above-described embodiment, as the liquid core material 4, for example, an ultraviolet curable resin material such as a UV epoxy resin material is used and cured by irradiating with ultraviolet rays, but is not limited thereto. For example, a photocurable resin material may be used as the liquid core material and cured by irradiation with light. Further, a thermosetting resin material may be used as the liquid core material and cured by applying heat.

  In the above-described embodiment, the present invention is applied to the multi-channel optical waveguide adapter 8 used for connecting the surface light emitting device array 32 and the surface light receiving device array 31 to the same optical fiber array 33 in the multi-channel optical transceiver. Although the case where it is applied is described as an example, the present invention is not limited to this. For example, in an optical transceiver, one light emitting device and one light receiving device are arranged in the same optical fiber array (consisting of two optical fibers). The present invention can also be applied to an optical waveguide adapter used to connect to the optical waveguide adapter.

In the above-described embodiment, the receiving-side optical waveguide 7B and the transmitting-side optical waveguide 7A are arranged such that the central axes of the optical waveguides 7A and 7B are aligned on the same plane at the end face on the side to which the optical fiber array 33 is connected. The step 6 is formed on the surface of the clad structure 1 between the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A, but is not limited thereto.
That is, from the viewpoint of the product, as in the above-described embodiment, there is a step 6 on the surface of the cladding structure 1 between the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A having different core sizes. Since the clad film (cover film) 5 tends to crack, it is desirable to ensure long-term reliability.

  Therefore, in order to prevent cracks from occurring in the clad film 5, for example, a step 6 is not formed on the surface between the reception side optical waveguide 7B and the transmission side optical waveguide 7A having different core sizes. As shown in FIG. 7, the stress applied to the clad film 5 is relieved by connecting the region where the reception side optical waveguide 7B is provided and the region where the transmission side optical waveguide 7A is provided by the inclined surface 10. preferable. In this case, the clad structure 1 has the inclined surface 10 on the surface between the reception side optical waveguide 7B and the transmission side optical waveguide 7A. 6 and 7, the same components as those in the first embodiment described above [see FIG. 5D and FIG. 2] are denoted by the same reference numerals.

  Further, for example, the step 6 formed on the surface between the reception side optical waveguide 7B and the transmission side optical waveguide 7A having different core sizes is left as it is, and the clad film (cover film) 5 is slit at a portion corresponding to the step 6. 8 or 9, the clad film (cover film) 5A, 5B divided into two parts is used, and a step 6 is formed so that a gap is formed in a portion corresponding to the step 6. It is also preferable that the clad film 5 be provided on both sides so that the clad film 5 is not distorted. In FIGS. 8 and 9, the same components as those in the first embodiment described above (see FIGS. 5D and 2) are denoted by the same reference numerals.

  In the above-described embodiment, the case where the present invention is applied to the optical waveguide structure 8 using the clad structure 1 having the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A formed on the curved surface 2 is taken as an example. However, the present invention is not limited to this. For example, as shown in FIG. 10, a reception-side optical waveguide (linear waveguide) 7BX and a transmission-side optical waveguide (linear waveguide) formed on the plane 12 are used. The present invention can also be applied to an optical waveguide structure using the clad structure 11 having 7AX. In FIG. 10, the same components as those in the first embodiment described above [see FIG. 2] are denoted by the same reference numerals.

Hereinafter, it demonstrates still in detail according to an Example. However, the present invention is not limited to the following examples.
In this example, an optical waveguide structure (polymer optical waveguide) having a reception side optical waveguide 7B and a transmission side optical waveguide 7A having different core sizes on the curved surface 2 by the manufacturing method (process flow) described in the above embodiment. 8 samples were prepared, and the coupling loss among the optical fiber array 33, the light receiving device 31A, and the light emitting device 32A was compared with the sample of the conventional structure.

  In this example, the transparent curved surface structure 1 was produced and used by injection molding (mold molding). That is, a molded body in which a curved surface (1/4 arc) having a curvature radius of 5 mm is a convex surface, and eight grooves (waveguide grooves) 3A and 3B are formed in parallel along the curved surface 2 constituting the convex surface. Used as the curved structure 1. Polyolefin was used as the material. The refractive index at a wavelength of 850 nm was 1.50.

Here, as the eight grooves, four grooves (reception-side waveguide grooves) 3B having a cross-sectional shape of 0.050 mm in length × 0.050 mm in width are formed in parallel at a pitch of 0.25 mm, and a length of 0. Four grooves (transmission-side waveguide grooves) 3A having a cross-sectional shape of 034 mm × lateral 0.034 mm were formed in parallel at a pitch of 0.25 mm.
Further, as will be described later, the central axis (the central axis of the reception-side optical waveguide 7B) 4B and the transmission-side waveguide groove 3A of the waveguide core (core of the reception-side optical waveguide 7B) formed in the reception-side waveguide groove 3B. And the central axis of the waveguide core (core of the transmission side optical waveguide 7A) 4A formed on the same plane (the central axis of the transmission side optical waveguide 7A) are aligned on the same plane [see FIGS. 1A and 1B], The central axes of the optical waveguides 7A and 7B coincide with the central axes of the optical fibers 33A constituting the optical fiber array 33 (here, a fiber array having 12 optical fibers 33A at a pitch of 0.25 mm) [FIG. 2 (B)], the bottom of the receiving-side waveguide groove 3B having a cross-sectional shape of 0.050 mm in length × 0.050 mm in width is the transmission-side waveguide groove having a cross-sectional shape of 0.034 mm in length × 0.034 mm in width. It is 0.008mm from the bottom of 3A It was formed at a deep position [see FIG. 2 (A)]. Accordingly, on the curved surface 2 of the curved surface structure 1, a region where the reception-side waveguide groove 3B is formed (the surface of the reception-side optical waveguide 7B) and a region where the transmission-side waveguide groove 3A is formed ( A step 6 of 0.008 mm was formed between the optical waveguide 7A and the transmission-side optical waveguide 7A (see FIG. 2A).

  Furthermore, when producing the curved surface structure 1 by injection molding as described above, hemispherical lenses 9 that are convex outward are simultaneously formed on both end faces of the grooves 3A and 3B [see FIG. 2 (B)]. The diameter of the lens 9 is 0.25 mm, the distance between the lens 9 and the ends of the grooves 3A and 3B is 0.5 mm, and the focal length of the lens 9 (the distance between the lens 9 and the optical fiber 33A) is 0. .5 mm [see FIG. 2 (B)].

As the core liquid (polymer liquid) 4 for filling, an ultraviolet curable epoxy resin having a refractive index after curing of 1.55 was used.
A film (transparent film; olefin film) made of polyolefin and having a thickness of 0.05 mm was used as the clad film 5 covering the upper portions of the grooves (waveguide grooves) 3A and 3B filled with the core liquid 4. The refractive index at a wavelength of 850 nm was 1.50.

Using these, a sample of the optical waveguide structure 8 was produced as follows.
First, for example, 0.1 cc of the core liquid 4 was dropped into the groove portion on the curved surface 2 of the transparent curved surface structure 1 by a quantitative dispenser.
Next, the core liquid 4 was completely filled in the grooves 3A and 3B while the clad film 5 was pressed against the surface thereof, and at the same time, the core liquid 4 other than the grooves 3A and 3B was removed.

In this state, the core liquid 4 was irradiated with ultraviolet rays and semi-cured. Although the core liquid 4 is semi-cured here, it may be cured at this stage.
And this was put into oven and heated at 120 degreeC for 60 minutes, the core liquid 4 was fully hardened, and waveguide core 4A, 4B was formed.
In this manner, a sample of the optical waveguide structure 8 including the reception-side optical waveguide 7B and the transmission-side optical waveguide 7A on the curved surface 2 was produced.

  On the other hand, a sample having a conventional structure was also prepared as a comparative example. That is, all of the eight grooves have a cross-sectional shape of 0.050 mm in length × 0.050 mm in width, and other than that, the same transparent curved surface structure and all of the eight grooves have a length of 0.034 mm × width. Two types of transparent curved surface structures having the same cross-sectional shape of 0.034 mm and the same transparent curved surface structure were prepared. Then, the core liquid is dropped onto each of these transparent curved surface structures in the same manner as in the above-described embodiments, and the core liquid is filled in the groove while being covered with the clad film, and then the core liquid is cured, and 2 Samples of various conventional structures were made. A sample having a cross-sectional shape of 0.050 mm in length and 0.050 mm in width is called a first sample, and a sample having a cross-sectional shape of 0.034 mm in length and 0.034 mm in width is called a second sample.

The samples thus obtained were evaluated as follows.
The coupling loss on the transmission side was evaluated as follows.
A surface-emitting laser 32A having a wavelength of 850 nm is used as a light source, and the samples prepared as described above are aligned and placed on the light-emitting surface 32AX (emission diameter 15 μm) of the surface-emitting laser 32A. The light that came out on the opposite side was received by an aligned multimode optical fiber (core diameter 0.050 mm) 33A, and the output was measured with an optical power meter.

Evaluation of the coupling loss on the receiving side was performed as follows.
Light from an external light source with a wavelength of 850 nm is guided to the end face on the optical fiber side of each sample prepared as described above through a multimode optical fiber (core diameter 0.050 mm), and passes through each sample to be opposite. The light which came out to the side was received by the aligned multimode optical fiber (core diameter 0.10 mm), and the output was measured with an optical power meter. Here, in order to measure the coupling loss more accurately, the coupling loss is received by an optical fiber having a core having the same diameter as that of the light receiving surface 31AX (diameter 0.10 mm) of the photodetector (light receiving element) 31A. The output is measured.

  As a result, as shown in FIG. 11, the coupling loss on the transmission side when the sample of this example is used is about 0.8 to 1.2 dB lower than that when the first sample is used. . Further, the coupling loss on the receiving side when using the sample of this example was lower by about 0.7 to 1.0 dB than when using the second sample. Thus, it was confirmed that the coupling loss can be suppressed on the receiving side and the transmitting side by using the sample of this example. Further, by using the sample of this example, the amount of light emitted from other waveguide cores (the amount of light emitted from leakage light) is in the range of −30 to −35 dB of the amount of incident light, and noise (crosstalk noise) ) Could be reduced.

  Next, as a sample of another embodiment, there is no step 6 on the surface between the receiving-side optical waveguide 7B and the transmitting-side optical waveguide 7A having different core sizes, and the inclined surface 10 is otherwise the same curved surface. A sample (see FIGS. 6 and 7) manufactured using the structure 1 in the same manner as in the above-described embodiment, and the same curved structure 1 as that in the above-described embodiment are arranged on both sides with a step 6 therebetween. Two samples of samples (see FIG. 8 and FIG. 9) prepared by the same method as in the above-described embodiment except that the two clad films 5A and 5B are covered, and the above-described examples are prepared. Compared with the sample of Example 1, the rate of occurrence of cracks (crack rate) generated in the clad film immediately after production was evaluated.

  As shown in FIG. 12, in the sample of the above-described example (first example), cracks were observed in 6 out of 20 samples, and the crack generation rate was 30%. On the other hand, in the sample of another example (second example) in which the curved structure has an inclined surface, cracks were observed in 2 out of 20 samples, and the crack occurrence rate was 10%. Further, in the sample of the other example (third example) in which the clad film was divided into two, no crack was observed in 20 samples, and the crack occurrence rate was 0%. Thus, it was confirmed that the configurations of the two other examples had an effect of suppressing the occurrence of cracks. Moreover, it has confirmed that the structure which does not provide a clad film on a level | step difference is especially effective in suppressing generation | occurrence | production of a crack.

Hereinafter, additional notes will be disclosed regarding the above-described embodiment.
(Appendix 1)
A receiving-side optical waveguide connecting a receiving optical fiber and a light receiving device included in the optical fiber array;
A transmission-side optical waveguide that connects a transmission optical fiber and a light-emitting device included in the optical fiber array;
An optical waveguide structure, wherein a cross-sectional area of a core of the reception-side optical waveguide is larger than a cross-sectional area of a core of the transmission-side optical waveguide.

(Appendix 2)
The shortest distance of the cross section of the core of the receiving optical waveguide is equal to or larger than the diameter of the core of the receiving optical fiber,
The optical waveguide structure according to appendix 1, wherein the longest distance of the cross section of the core of the transmission-side optical waveguide is equal to or smaller than the diameter of the core of the transmission optical fiber.

(Appendix 3)
The longest distance of the cross section of the core of the receiving side optical waveguide is equal to or smaller than the diameter of the light receiving surface of the light receiving device,
The optical waveguide structure according to appendix 1 or 2, wherein a shortest distance of a cross section of a core of the transmission side optical waveguide is equal to or larger than a diameter of a light emitting surface of the light emitting device.

(Appendix 4)
The receiving-side optical waveguide and the transmitting-side optical waveguide are arranged such that the central axes of the optical waveguide are aligned on the same plane at the end face on the side to which the optical fiber array is connected, and each optical fiber constituting the optical fiber array The optical waveguide structure according to any one of appendices 1 to 3, wherein the optical waveguide structure is provided so as to coincide with an interval between the central axes.

(Appendix 5)
A clad structure having grooves of different sizes formed on a curved surface;
A waveguide core formed in the groove;
A clad film covering the waveguide core;
The optical waveguide according to any one of appendices 1 to 4, wherein the reception-side optical waveguide and the transmission-side optical waveguide are configured by the cladding structure, the waveguide core, and the cladding film. Structure.

(Appendix 6)
A clad structure having grooves of different sizes formed on a curved surface;
A waveguide core formed in the groove;
A clad film covering the waveguide core;
The reception-side optical waveguide and the transmission-side optical waveguide are constituted by the cladding structure, the waveguide core, and the cladding film,
The receiving-side optical waveguide and the transmitting-side optical waveguide are arranged such that the central axes of the optical waveguide are aligned on the same plane at the end face on the side to which the optical fiber array is connected, and each optical fiber constituting the optical fiber array It is provided so as to match the interval of the central axis of
The optical waveguide structure according to any one of appendices 1 to 3, wherein the cladding structure has a step on a surface between the reception-side optical waveguide and the transmission-side optical waveguide.

(Appendix 7)
Additional note 6, wherein the clad film has a slit at a part corresponding to the step, or the clad film is divided into two parts and is provided on both sides of the step. Optical waveguide structure.
(Appendix 8)
A clad structure having grooves of different sizes formed on a curved surface;
A waveguide core formed in the groove;
A clad film covering the waveguide core;
The reception-side optical waveguide and the transmission-side optical waveguide are constituted by the cladding structure, the waveguide core, and the cladding film,
The receiving-side optical waveguide and the transmitting-side optical waveguide are arranged such that the central axes of the optical waveguide are aligned on the same plane at the end face on the side to which the optical fiber array is connected, and each optical fiber constituting the optical fiber array It is provided so as to match the interval of the central axis of
The optical waveguide structure according to any one of appendices 1 to 3, wherein the clad structure has a slope on a surface between the reception-side optical waveguide and the transmission-side optical waveguide.

(Appendix 9)
An optical module comprising the optical waveguide structure according to any one of appendices 1 to 8.
(Appendix 10)
An optical waveguide comprising: a receiving-side optical waveguide that connects a receiving optical fiber and a light-receiving device included in the optical fiber array; and a transmitting-side optical waveguide that connects the transmitting optical fiber and the light-emitting device included in the optical fiber array. A structure manufacturing method comprising:
Producing a clad structure having grooves of different sizes on the curved surface such that the cross-sectional area of the core of the receiving-side optical waveguide is larger than the cross-sectional area of the core of the transmitting-side optical waveguide;
Filling the groove with a liquid core material and covering the groove with a cladding film;
And a step of curing the liquid core material in a state covered with the clad film.

(A) is typical sectional drawing (sectional drawing in alignment with the central-axis direction of an optical waveguide) which shows the structure of the optical waveguide structure concerning one Embodiment of this invention, (B) is one Embodiment of this invention. Schematic cross section showing the relationship between the cross-sectional shape of the optical waveguide included in the optical waveguide structure according to the embodiment (the cross-sectional shape along the direction orthogonal to the central axis of the optical waveguide) and the cross-sectional shape of the optical fiber included in the optical fiber array FIG. (A) is typical sectional drawing (sectional drawing in alignment with the direction orthogonal to the central axis of an optical waveguide) which shows the structure of the optical waveguide structure concerning one Embodiment of this invention, (B) is this invention. Schematic sectional view showing the configuration of the optical waveguide structure according to one embodiment (sectional view along the central axis direction of the optical waveguide), and schematic sectional view showing the configuration of the optical fiber array (central axis of the optical fiber) It is sectional drawing along a direction). (A) is the relationship between the cross-sectional shape (cross-sectional shape along the direction orthogonal to the center axis | shaft of an optical waveguide) of the optical waveguide contained in the optical waveguide structure concerning one Embodiment of this invention, and the light-receiving surface shape of a light-receiving device. FIG. 5B is a schematic diagram illustrating a cross-sectional shape of an optical waveguide included in the optical waveguide structure according to an embodiment of the present invention (a cross-sectional shape along a direction perpendicular to the central axis of the optical waveguide) and a light-emitting device. It is a schematic diagram which shows the relationship with the light emission surface shape. It is a typical perspective view for demonstrating the multichannel optical transceiver (optical module) using the optical waveguide structure concerning one Embodiment of this invention. (A)-(D) are the figures for demonstrating the manufacturing method of the optical waveguide structure concerning one Embodiment of this invention. It is a typical perspective view which shows the structure of the optical waveguide structure concerning the modification of one Embodiment of this invention. (A) is typical sectional drawing (sectional drawing which follows the direction orthogonal to the central axis of an optical waveguide) which shows the structure of the optical waveguide structure concerning the modification of one Embodiment of this invention, (B) , A schematic cross-sectional view showing a configuration of an optical waveguide structure according to a modification of one embodiment of the present invention (a cross-sectional view taken along the central axis direction of the optical waveguide), and a schematic cross-sectional view showing a configuration of an optical fiber array It is sectional drawing which follows the central-axis direction of an optical fiber. It is a typical perspective view which shows the structure of the optical waveguide structure concerning the other modification of one Embodiment of this invention. (A) is typical sectional drawing (sectional drawing which follows the direction orthogonal to the central axis of an optical waveguide) which shows the structure of the optical waveguide structure concerning the other modification of one Embodiment of this invention, (B ) Shows a schematic cross-sectional view (cross-sectional view along the central axis direction of the optical waveguide) showing the configuration of the optical waveguide structure according to another modification of the embodiment of the present invention, and shows the configuration of the optical fiber array. It is typical sectional drawing (sectional drawing in alignment with the central-axis direction of an optical fiber). (A) is typical sectional drawing (sectional drawing which follows the direction orthogonal to the central axis of an optical waveguide) which shows the structure of the optical waveguide structure concerning the other modification of one Embodiment of this invention, (B ) Is a schematic perspective view showing a configuration of an optical waveguide structure according to another modification of the embodiment of the present invention. It is a figure which shows the result of having measured each coupling loss of the sample of the optical waveguide structure concerning one Example of this invention, and the 1st sample and 2nd sample as a comparative example. It is a figure which shows the result of having measured each coupling loss of the sample of the optical waveguide structure concerning one Example of this invention, and the 1st sample and 2nd sample as a comparative example. (A), (B) is typical sectional drawing for demonstrating the subject of this invention.

Explanation of symbols

1 Curved structure (clad structure)
2 Curved surface (convex surface)
3A Transmission side groove (Guide groove)
3B Reception side groove (waveguide groove)
4 Liquid Core Material 4A Transmission Side Waveguide Core 4B Reception Side Waveguide Core 5, 5A, 5B Clad Film 6 Step 7A Transmission Side Optical Waveguide (Curve Waveguide)
7B Receiver optical waveguide (curved waveguide)
7AX Transmission-side optical waveguide (straight waveguide)
7BX Receiving side optical waveguide (straight waveguide)
8 Optical waveguide structure (polymer optical waveguide)
9 Lens 10 Slope 11 Planar structure (cladding structure)
12 Plane 30 Printed circuit board (circuit board)
31 Surface light receiving element array (PD array chip)
31A Light Receiving Device 31AX Light Receiving Surface 32 Planar Light Emitting Element Array (VCSEL Array Chip)
32A light emitting device 32AX light emitting surface 33 optical fiber array (ribbon fiber)
33A Optical fiber 34 Optical connector 35 Driver IC
36 Receiver IC

Claims (5)

A receiving-side optical waveguide connecting a receiving optical fiber and a light receiving device included in the optical fiber array;
A transmission-side optical waveguide that connects a transmission optical fiber and a light-emitting device included in the optical fiber array;
An optical waveguide structure, wherein a cross-sectional area of a core of the reception-side optical waveguide is larger than a cross-sectional area of a core of the transmission-side optical waveguide. The shortest distance of the cross section of the core of the receiving optical waveguide is equal to or larger than the diameter of the core of the receiving optical fiber,
2. The optical waveguide structure according to claim 1, wherein a longest distance of a cross section of a core of the transmission-side optical waveguide is equal to or smaller than a diameter of the core of the transmission optical fiber. The longest distance of the cross section of the core of the receiving side optical waveguide is equal to or smaller than the diameter of the light receiving surface of the light receiving device,
3. The optical waveguide structure according to claim 1, wherein a shortest distance of a cross section of a core of the transmission-side optical waveguide is equal to or larger than a diameter of a light emitting surface of the light emitting device.   An optical module comprising the optical waveguide structure according to claim 1. An optical waveguide comprising: a receiving-side optical waveguide that connects a receiving optical fiber and a light-receiving device included in the optical fiber array; and a transmitting-side optical waveguide that connects the transmitting optical fiber and the light-emitting device included in the optical fiber array. A structure manufacturing method comprising:
Producing a clad structure having grooves of different sizes on the curved surface such that the cross-sectional area of the core of the receiving-side optical waveguide is larger than the cross-sectional area of the core of the transmitting-side optical waveguide;
Filling the groove with a liquid core material and covering the groove with a cladding film;
And a step of curing the liquid core material in a state covered with the clad film.

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